This invention relates, generally, to suspended cable transport systems commonly known as zip lines and, more particularly, to trolleys for downhill zip line systems which are securely attached to the suspended cable and are designed to control maximum descent speed within a safe range.
Transport systems involving a trolley slidable along a suspended length of cable have been known in the art for many years. Commonly known as zip lines, such systems are extensively used for rescue work on ski lift equipment. They are also available as backyard toys for children and adults. Spring Swings, Inc. of Riviera Beach, Fla., manufactures a Fun Ride Deluxe Zip Line kit which can be installed between two trees or other suitable cable supports. The kit includes enough stranded steel aircraft cable for a ride of about 21 meters (70 feet) in length, cable tensioning devices, and a xe2x80x9csuper toughxe2x80x9d double-pulley plastic trolley which travels bidirectionally on the suspended cable. The kit retails for less than $100.
Within the past decade, zip lines have become part of the xe2x80x9cextreme sportsxe2x80x9d scene. One particular zip line installed on a hill in the Costa Rican jungle has been given rave reviews. The Costa Rican system is really quite primitive, having a trolley with a single deep-groove nylon pulley riding on the suspended cable. In order to slow his descent, a rider must twist the trolley, thereby causing the flanges of the pulley to rub against the cable and generate friction. Kinetic energy is, thus, dissipated as heat. Riders who are particularly heavy may generate so much friction and related heat that the trolley pulley may fail prematurely. Such a system is potentially dangerous, as the riders, themselves, must take responsibility for maintaining their descent speeds within a safe range, in order to avoid smashing into the lower cable support tower. In the absence of a legal system which demands that even the most risk-inclined, incompetent and moronic individuals be protected from themselves, such a zip line system might operate in perpetuity. However, in a country such as the U.S., the slip and fall plaintiffs"" bar would kill it almost immediately.
Within the past year, a sophisticated, safe, and thoroughly-engineered zip line thrill ride was installed on a steep hill at Park City, Utah. The suspended cable is about 805 meters in length (0.5 mile), and the vertical drop is approximately 183 meters (600 feet). Although maximum speeds in excess of 90 m.p.h. are attainable on the system, the maximum speed experienced by paying riders is automatically limited by the equipment to no more than about 55 m.p.h. Certain components and features of this modern zip line system are the subjects of this patent.
The zip line thrill ride system that is the focus of this invention includes a cable suspended between a upper cable support tower and platform which, together, function as the harnessing, loading, and take-off point for the ride, and a lower cable support tower and platform which, together, function as the landing, unloading and unharnessing point of the ride. Multiple, substantially identical trolleys are designed to quickly engage and disengage the cable. A safety lock actuated by ride operator personnel at the loading point prevents the trolley from being removed from the cable until it is unlocked at the unloading point by ride operator personnel at the landing point. The trolley, the structural components of which are fabricated almost entirely from stainless steel, includes a frame of generally I-beam cross section fabricated from metal plate stock. A generally tubular brake retainer, having a longitudinal slit therein, is welded to an upper rear portion of the frame. A grooved, generally cylindrical brake fabricated from a durable polymeric material, such as Teflon(copyright), nylon, or high-density polyethylene, high density polyethylene (HDPE) brake, is rotatably affixed within the tubular brake retainer. When the trolley is affixed to the suspended cable, the grooved insert rides against the suspended cable and functions as a brake. A clevis/handle assembly is bolted to a central portion of the frame. A pulley is rotatably mounted within the clevis. The clevis bracket of the clevis/handle assembly is positioned so that a lower portion of the pulley is exposed.
In order to attach the trolley to the suspended cable, the brake is rotated so that its groove coincides with the slit of the tubular brake retainer. The trolley is then positioned below and oblique or perpendicular to the suspended cable. The trolley is then elevated so that the cable enters the gap between the brake retainer and the clevis/handle assembly. Once the cable is positioned below the level of the pulley flanges, the trolley is rotated so that the cable enters the slit of the brake retainer and the groove of the brake and the pulley is positioned over the cable. The trolley is then lowered to seat the pulley on the cable. The brake is then rotated so that the groove therein faces upward, thereby locking the suspended cable within the tubular brake retainer.
The frame also includes a longitudinal slot forward of the clevis/handle assembly mounting point that is generally parallel to the axis of the tubular brake retainer. The frame also includes a linear array of evenly-spaced apertures that is beneath and parallel to the longitudinal slot. A lever arm adjustment bracket is attached to the frame with a retainer pin that passes through both arms of the U-shaped suspension bracket, allowing the lever arm adjustment bracket to be moved back and forth within the longitudinal slot. The suspension bracket has a pair of locking apertures, which are alignable with any of the apertures in the linear array. The lever arm adjustment bracket may be locked in place by inserting a locking pin through the pair of locking apertures and through one of the apertures in the linear array. The farther forward the lever arm adjustment bracket is located, the greater the pressure applied by the brake to the suspension cable. The position of the lever arm adjustment bracket is selected in accordance with the weight of the rider and the maximum desired speed of the ride. Thus, for any rider, the closer the lever arm adjustment bracket is to the handle/clevis assembly, the greater the maximum speed. Conversely, the farther the lever arm adjustment bracket is from the handle/clevis assembly, the slower the maximum speed.
The nose of the frame is downwardly slanted and has mounted thereon a bumper made of a durable polymeric material such as Teflon(copyright), nylon, or high-density polyethylene. At the end of the ride, the nose engages a V-shaped trap that is slidable on the suspended cable against one or more unloaded coil springs that are concentrically installed on weighted bushings on the suspended cable. As the nose of the frame engages the V-shaped trap, it is pushed down, thereby increasing the pressure between the brake and the suspended cable and, at the same time, accelerating the weighted bushings and compressing the coil springs. These features ensure that even if the pressure of the brake against the suspended cable is not properly adjusted before the ride begins, the rider will stop safely before reaching the end of the suspended cable.